Im on birth control and Trileptal (Oxcarbazepine). how much less effective is my bc?

it says that it makes it less effective but it doesn't tell ya how much less effective.. this is really annoying why cant it give us numbers!! anyone know what the chances of pregnancy are while using trileptal and birth control?

I was on bc for a while and switched to an IUD after I got pregnant on the bc. It does make it ineffective. My dr switched my bc to a higher dosage one that supposedly was not going to have issues... welll-not true. I ended up terminating the pregnancy, because the known issues were only from research done in rats-and those were not good, and there were too many unknown effects on the fetus. Neither my Gyn nor my Neurologist could find much. Good luck.